(crawler) Improve deferred task behavior

The previous icon was of an irregular size and shifted the layout in an unaesthetic way.

code/common/service/java/nu/marginalia/service/module/ServiceConfigurationModule.java

@@ -121,6 +121,7 @@ public class ServiceConfigurationModule extends AbstractModule {
 
         while (nets.hasMoreElements()) {
             NetworkInterface netif = nets.nextElement();
+            logger.info("Considering network interface {}:  Up? {},  Loopback? {}", netif.getDisplayName(), netif.isUp(), netif.isLoopback());
             if (!netif.isUp() || netif.isLoopback()) {
                 continue;
             }
@@ -128,6 +129,7 @@ public class ServiceConfigurationModule extends AbstractModule {
             Enumeration<InetAddress> inetAddresses = netif.getInetAddresses();
             while (inetAddresses.hasMoreElements()) {
                 InetAddress addr = inetAddresses.nextElement();
+                logger.info("Considering address {}: SiteLocal? {}, Loopback? {}", addr.getHostAddress(), addr.isSiteLocalAddress(), addr.isLoopbackAddress());
                 if (addr.isSiteLocalAddress() && !addr.isLoopbackAddress()) {
                     return addr.getHostAddress();
                 }

code/common/service/java/nu/marginalia/service/server/JoobyService.java

@@ -15,6 +15,7 @@ import org.slf4j.LoggerFactory;
 import org.slf4j.Marker;
 import org.slf4j.MarkerFactory;
 
+import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.List;
@@ -106,9 +107,12 @@ public class JoobyService {
                 config.externalAddress());
 
         // FIXME:  This won't work outside of docker, may need to submit a PR to jooby to allow classpaths here
-        jooby.install(new JteModule(Path.of("/app/resources/jte"), Path.of("/app/classes/jte-precompiled")));
-        jooby.assets("/*", Paths.get("/app/resources/static"));
-
+        if (Files.exists(Path.of("/app/resources/jte")) || Files.exists(Path.of("/app/classes/jte-precompiled"))) {
+            jooby.install(new JteModule(Path.of("/app/resources/jte"), Path.of("/app/classes/jte-precompiled")));
+        }
+        if (Files.exists(Path.of("/app/resources/static"))) {
+            jooby.assets("/*", Paths.get("/app/resources/static"));
+        }
         var options = new ServerOptions();
         options.setHost(config.bindAddress());
         options.setPort(restEndpoint.port());

code/common/service/java/nu/marginalia/service/server/MetricsServer.java

@@ -13,7 +13,7 @@ import java.net.InetSocketAddress;
 
 public class MetricsServer {
 
-    private static Logger logger = LoggerFactory.getLogger(MetricsServer.class);
+    private static final Logger logger = LoggerFactory.getLogger(MetricsServer.class);
 
     @Inject
     public MetricsServer(ServiceConfiguration configuration) {
@@ -30,6 +30,8 @@ public class MetricsServer {
 
             context.addServlet(new ServletHolder(new MetricsServlet()), "/metrics");
 
+            logger.info("MetricsServer listening on {}:{}", configuration.bindAddress(), configuration.metricsPort());
+
             server.start();
         }
         catch (Exception|NoSuchMethodError ex) {

code/processes/converting-process/model/java/nu/marginalia/model/processed/SlopDocumentRecord.java

@@ -11,7 +11,6 @@ import nu.marginalia.slop.column.primitive.IntColumn;
 import nu.marginalia.slop.column.primitive.LongColumn;
 import nu.marginalia.slop.column.string.EnumColumn;
 import nu.marginalia.slop.column.string.StringColumn;
-import nu.marginalia.slop.column.string.TxtStringColumn;
 import nu.marginalia.slop.desc.StorageType;
 import org.jetbrains.annotations.Nullable;
 
@@ -182,8 +181,8 @@ public record SlopDocumentRecord(
     }
 
     // Basic information
-    private static final TxtStringColumn domainsColumn = new TxtStringColumn("domain", StandardCharsets.UTF_8, StorageType.GZIP);
-    private static final TxtStringColumn urlsColumn = new TxtStringColumn("url", StandardCharsets.UTF_8, StorageType.GZIP);
+    private static final StringColumn domainsColumn = new StringColumn("domain", StandardCharsets.UTF_8, StorageType.GZIP);
+    private static final StringColumn urlsColumn = new StringColumn("url", StandardCharsets.UTF_8, StorageType.GZIP);
     private static final VarintColumn ordinalsColumn = new VarintColumn("ordinal", StorageType.PLAIN);
     private static final EnumColumn statesColumn = new EnumColumn("state", StandardCharsets.US_ASCII, StorageType.PLAIN);
     private static final StringColumn stateReasonsColumn = new StringColumn("stateReason", StandardCharsets.US_ASCII, StorageType.GZIP);
@@ -211,7 +210,7 @@ public record SlopDocumentRecord(
     private static final VarintCodedSequenceArrayColumn spansColumn = new VarintCodedSequenceArrayColumn("spans", StorageType.ZSTD);
 
     public static class KeywordsProjectionReader extends SlopTable {
-        private final TxtStringColumn.Reader domainsReader;
+        private final StringColumn.Reader domainsReader;
         private final VarintColumn.Reader ordinalsReader;
         private final IntColumn.Reader htmlFeaturesReader;
         private final LongColumn.Reader domainMetadataReader;
@@ -275,8 +274,8 @@ public record SlopDocumentRecord(
     }
 
     public static class MetadataReader extends SlopTable {
-        private final TxtStringColumn.Reader domainsReader;
-        private final TxtStringColumn.Reader urlsReader;
+        private final StringColumn.Reader domainsReader;
+        private final StringColumn.Reader urlsReader;
         private final VarintColumn.Reader ordinalsReader;
         private final StringColumn.Reader titlesReader;
         private final StringColumn.Reader descriptionsReader;
@@ -332,8 +331,8 @@ public record SlopDocumentRecord(
     }
 
     public static class Writer extends SlopTable {
-        private final TxtStringColumn.Writer domainsWriter;
-        private final TxtStringColumn.Writer urlsWriter;
+        private final StringColumn.Writer domainsWriter;
+        private final StringColumn.Writer urlsWriter;
         private final VarintColumn.Writer ordinalsWriter;
         private final EnumColumn.Writer statesWriter;
         private final StringColumn.Writer stateReasonsWriter;

code/processes/crawling-process/java/nu/marginalia/crawl/CrawlerMain.java

@@ -248,9 +248,14 @@ public class CrawlerMain extends ProcessMainClass {
             // (this happens when the process is restarted after a crash or a shutdown)
             tasksDone.set(workLog.countFinishedJobs());
 
-            // Create crawl tasks and submit them to the pool for execution
+            // List of deferred tasks used to ensure beneficial scheduling of domains with regard to DomainLocks,
+            // merely shuffling the domains tends to lead to a lot of threads being blocked waiting for a semphore,
+            // this will more aggressively attempt to schedule the jobs to avoid blocking
+            List<CrawlTask> taskList = new ArrayList<>();
+
+            // Create crawl tasks
             for (CrawlSpecRecord crawlSpec : crawlSpecRecords) {
-                if (workLog.isJobFinished(crawlSpec.domain()))
+                if (workLog.isJobFinished(crawlSpec.domain))
                     continue;
 
                 var task = new CrawlTask(
@@ -261,11 +266,22 @@ public class CrawlerMain extends ProcessMainClass {
                         domainStateDb,
                         workLog);
 
-                if (pendingCrawlTasks.putIfAbsent(crawlSpec.domain(), task) == null) {
-                    pool.submitQuietly(task);
+                // Try to run immediately, to avoid unnecessarily keeping the entire work set in RAM
+                if (!trySubmitDeferredTask(task)) {
+                    // Otherwise add to the taskList for deferred execution
+                    taskList.add(task);
                 }
             }
 
+             // Schedule viable tasks for execution until list is empty
+            while (!taskList.isEmpty()) {
+                taskList.removeIf(this::trySubmitDeferredTask);
+
+                // Add a small pause here to avoid busy looping toward the end of the execution cycle when
+                // we might have no new viable tasks to run for hours on end
+                TimeUnit.MILLISECONDS.sleep(50);
+            }
+
             logger.info("Shutting down the pool, waiting for tasks to complete...");
 
             pool.shutDown();
@@ -290,6 +306,28 @@ public class CrawlerMain extends ProcessMainClass {
         }
     }
 
+    /** Submit a task for execution if it can be run, returns true if it was submitted
+     * or if it can be discarded */
+    private boolean trySubmitDeferredTask(CrawlTask task) {
+        if (!task.canRun()) {
+            return false;
+        }
+
+        if (pendingCrawlTasks.putIfAbsent(task.domain, task) != null) {
+            return true; // task has already run, duplicate in crawl specs
+        }
+
+        try {
+            // This blocks the caller when the pool is full
+            pool.submitQuietly(task);
+            return true;
+        }
+        catch (RuntimeException ex) {
+            logger.error("Failed to submit task " + task.domain, ex);
+            return false;
+        }
+    }
+
     public void runForSingleDomain(String targetDomainName, FileStorageId fileStorageId) throws Exception {
         runForSingleDomain(targetDomainName, fileStorageService.getStorage(fileStorageId).asPath());
     }
@@ -346,9 +384,20 @@ public class CrawlerMain extends ProcessMainClass {
             this.id = Integer.toHexString(domain.hashCode());
         }
 
+        /** Best effort indicator whether we could start this now without getting stuck in
+         * DomainLocks purgatory */
+        public boolean canRun() {
+            return domainLocks.canLock(new EdgeDomain(domain));
+        }
+
         @Override
         public void run() throws Exception {
 
+            if (workLog.isJobFinished(domain)) { // No-Op
+                logger.info("Omitting task {}, as it is already run", domain);
+                return;
+            }
+
             Path newWarcFile = CrawlerOutputFile.createWarcPath(outputDir, id, domain, CrawlerOutputFile.WarcFileVersion.LIVE);
             Path tempFile = CrawlerOutputFile.createWarcPath(outputDir, id, domain, CrawlerOutputFile.WarcFileVersion.TEMP);
             Path slopFile = CrawlerOutputFile.createSlopPath(outputDir, id, domain);
@@ -403,7 +452,7 @@ public class CrawlerMain extends ProcessMainClass {
                 logger.error("Error fetching domain " + domain, e);
             }
             finally {
-                // We don't need to double-count these; it's also kept int he workLog
+                // We don't need to double-count these; it's also kept in the workLog
                 pendingCrawlTasks.remove(domain);
                 Thread.currentThread().setName("[idle]");
 
@@ -494,7 +543,7 @@ public class CrawlerMain extends ProcessMainClass {
     //
     // This must be synchronized as chewing through parquet files in parallel leads to enormous memory overhead
     private synchronized Path migrateParquetData(Path inputPath, String domain, Path crawlDataRoot) throws IOException {
-        if (!inputPath.endsWith(".parquet")) {
+        if (!inputPath.toString().endsWith(".parquet")) {
             return inputPath;
         }
 

code/processes/crawling-process/java/nu/marginalia/crawl/fetcher/HttpFetcherImpl.java

@@ -251,6 +251,7 @@ public class HttpFetcherImpl implements HttpFetcher {
         return new SitemapRetriever();
     }
 
+    /** Recursively fetch sitemaps */
     @Override
     public List<EdgeUrl> fetchSitemapUrls(String root, CrawlDelayTimer delayTimer) {
         try {
@@ -270,7 +271,7 @@ public class HttpFetcherImpl implements HttpFetcher {
             while (!sitemapQueue.isEmpty() && ret.size() < 20_000 && ++fetchedSitemaps < 10) {
                 var head = sitemapQueue.removeFirst();
 
-                switch (fetchSitemap(head)) {
+                switch (fetchSingleSitemap(head)) {
                     case SitemapResult.SitemapUrls(List<String> urls) -> {
 
                         for (var url : urls) {
@@ -306,7 +307,7 @@ public class HttpFetcherImpl implements HttpFetcher {
     }
 
 
-    private SitemapResult fetchSitemap(EdgeUrl sitemapUrl) throws URISyntaxException, IOException, InterruptedException {
+    private SitemapResult fetchSingleSitemap(EdgeUrl sitemapUrl) throws URISyntaxException, IOException, InterruptedException {
         HttpRequest getRequest = HttpRequest.newBuilder()
                 .GET()
                 .uri(sitemapUrl.asURI())

code/processes/crawling-process/java/nu/marginalia/crawl/logic/DomainLocks.java

@@ -44,6 +44,14 @@ public class DomainLocks {
         return new Semaphore(2);
     }
 
+    public boolean canLock(EdgeDomain domain) {
+        Semaphore sem = locks.get(domain.topDomain.toLowerCase());
+        if (null == sem)
+            return true;
+        else
+            return sem.availablePermits() > 0;
+    }
+
     public static class DomainLock implements AutoCloseable {
         private final String domainName;
         private final Semaphore semaphore;

code/processes/crawling-process/model/java/nu/marginalia/io/SerializableCrawlDataStream.java

@@ -42,18 +42,20 @@ public interface SerializableCrawlDataStream extends AutoCloseable {
     {
 
         String fileName = fullPath.getFileName().toString();
-        if (fileName.endsWith(".parquet")) {
+
+        if (fileName.endsWith(".slop.zip")) {
             try {
-                return new ParquetSerializableCrawlDataStream(fullPath);
+                return new SlopSerializableCrawlDataStream(fullPath);
             } catch (Exception ex) {
                 logger.error("Error reading domain data from " + fullPath, ex);
                 return SerializableCrawlDataStream.empty();
             }
         }
 
-        if (fileName.endsWith(".slop.zip")) {
+        else if (fileName.endsWith(".parquet")) {
+            logger.error("Opening deprecated parquet-style crawl data stream", new Exception());
             try {
-                return new SlopSerializableCrawlDataStream(fullPath);
+                return new ParquetSerializableCrawlDataStream(fullPath);
             } catch (Exception ex) {
                 logger.error("Error reading domain data from " + fullPath, ex);
                 return SerializableCrawlDataStream.empty();

code/services-application/search-service-legacy/java/nu/marginalia/search/command/SearchJsParameter.java

@@ -7,8 +7,7 @@ import java.util.Arrays;
 
 public enum SearchJsParameter {
     DEFAULT("default"),
-    DENY_JS("no-js", "js:true"),
-    REQUIRE_JS("yes-js", "js:false");
+    DENY_JS("no-js", "special:scripts");
 
     public final String value;
     public final String[] implictExcludeSearchTerms;
@@ -20,7 +19,6 @@ public enum SearchJsParameter {
 
     public static SearchJsParameter parse(@Nullable String value) {
         if (DENY_JS.value.equals(value)) return DENY_JS;
-        if (REQUIRE_JS.value.equals(value)) return REQUIRE_JS;
 
         return DEFAULT;
     }

code/services-application/search-service/java/nu/marginalia/search/command/SearchJsParameter.java

@@ -7,9 +7,7 @@ import java.util.Arrays;
 
 public enum SearchJsParameter {
     DEFAULT("default"),
-    DENY_JS("no-js", "js:true"),
-    REQUIRE_JS("yes-js", "js:false");
-
+    DENY_JS("no-js", "special:scripts");
     public final String value;
     public final String[] implictExcludeSearchTerms;
 
@@ -20,7 +18,6 @@ public enum SearchJsParameter {
 
     public static SearchJsParameter parse(@Nullable String value) {
         if (DENY_JS.value.equals(value)) return DENY_JS;
-        if (REQUIRE_JS.value.equals(value)) return REQUIRE_JS;
 
         return DEFAULT;
     }

code/services-application/search-service/java/nu/marginalia/search/model/DecoratedSearchResults.java

@@ -67,6 +67,10 @@ public class DecoratedSearchResults {
         return focusDomainId >= 0;
     }
 
+    public boolean isEmpty() {
+        return results.isEmpty();
+    }
+
     public SearchFilters getFilters() {
         return filters;
     }

code/services-application/search-service/java/nu/marginalia/search/model/SearchFilters.java

@@ -81,6 +81,7 @@ public class SearchFilters {
                             ),
                             List.of(
                                     new Filter("Vintage", "fa-clock-rotate-left", SearchProfile.VINTAGE, parameters),
+                                    new Filter("Small Web", "fa-minus", SearchProfile.SMALLWEB, parameters),
                                     new Filter("Plain Text", "fa-file", SearchProfile.PLAIN_TEXT, parameters),
                                     new Filter("Tilde", "fa-house", SearchProfile.TILDE, parameters)
                             ),

code/services-application/search-service/resources/jte/part/testenvHead.jte

@@ -9,6 +9,14 @@
                     nicotine: '#f8f8ee',
                     margeblue: '#3e5f6f',
                     liteblue: '#0066cc',
+                },
+                screens: {
+                    'coarsepointer': {
+                        'raw': '(pointer: coarse)'
+                    },
+                    'finepointer': {
+                        'raw': '(pointer: fine)'
+                    },
                 }
             },
             screens: {

code/services-application/search-service/resources/jte/serp/main.jte

@@ -23,7 +23,7 @@
                 @template.serp.part.searchform(query = results.getParams().query(), profile = results.getProfile(), filters = results.getFilters())
             </div>
             <div class="grow"></div>
-            <button class="fixed bottom-10 right-5 sm:hidden text-sm bg-margeblue text-white p-4 rounded-xl active:text-slate-200" id="filter-button">
+            <button class="fixed bottom-10 right-5 finepointer:hidden md:hidden text-sm bg-margeblue text-white p-4 rounded-xl active:text-slate-200" id="filter-button">
                 <i class="fas fa-filter mr-3"></i>
                 Filters
             </button>
@@ -44,6 +44,11 @@
                 <div class="grow"></div>
                 <a href="${results.getParams().renderUrlWithoutSiteFocus()}" class="fa fa-remove"></a>
             </div>
+        @elseif (results.isEmpty())
+            <div class="border dark:border-gray-600 rounded flex space-x-4 bg-white dark:bg-gray-800 text-gray-600 dark:text-gray-100 text-sm p-4 items-center">
+                No search results found.  Try different search terms, or spelling variations.  The search engine currently
+                only supports queries in the English language.
+            </div>
         @endif
 
         <div class="space-y-4 sm:space-y-6">

code/services-application/search-service/resources/jte/serp/part/sidebar.jte

@@ -3,7 +3,7 @@
 
 @param SearchFilters filters
 
-<aside class="md:w-64 py-4 shrink-0 hidden sm:block">
+<aside class="md:w-64 py-4 shrink-0 hidden md:block finepointer:block">
     <div class="space-y-6 sticky top-4">
         <div class="bg-white dark:bg-gray-800 p-4 border dark:border-gray-600 border-gray-300">
             <h2 class="font-medium mb-3 flex items-center font-serif hidden md:block">

code/services-application/search-service/tailwind/tailwind.config.js

@@ -9,6 +9,14 @@ module.exports = {
         nicotine: '#f8f8ee',
         margeblue: '#3e5f6f',
         liteblue: '#0066cc',
+      },
+      screens: {
+        'coarsepointer': {
+          'raw': '(pointer: coarse)'
+        },
+        'finepointer': {
+          'raw': '(pointer: fine)'
+        },
       }
     },
     screens: {

code/services-core/assistant-service/build.gradle

@@ -37,8 +37,6 @@ dependencies {
     implementation project(':code:functions:domain-info')
     implementation project(':code:functions:domain-info:api')
 
-    implementation project(':code:features-search:screenshots')
-
     implementation project(':code:libraries:geo-ip')
     implementation project(':code:libraries:language-processing')
     implementation project(':code:libraries:term-frequency-dict')
@@ -48,6 +46,7 @@ dependencies {
 
     implementation libs.bundles.slf4j
     implementation libs.prometheus
+    implementation libs.commons.io
     implementation libs.guava
     libs.bundles.grpc.get().each {
         implementation dependencies.create(it) {
@@ -61,9 +60,7 @@ dependencies {
     implementation dependencies.create(libs.guice.get()) {
         exclude group: 'com.google.guava'
     }
-    implementation dependencies.create(libs.spark.get()) {
-        exclude group: 'org.eclipse.jetty'
-    }
+    implementation libs.bundles.jooby
     implementation libs.bundles.jetty
     implementation libs.opencsv
     implementation libs.trove

code/services-core/assistant-service/java/nu/marginalia/assistant/AssistantMain.java

@@ -3,6 +3,8 @@ package nu.marginalia.assistant;
 import com.google.inject.Guice;
 import com.google.inject.Inject;
 import com.google.inject.Injector;
+import io.jooby.ExecutionMode;
+import io.jooby.Jooby;
 import nu.marginalia.livecapture.LivecaptureModule;
 import nu.marginalia.service.MainClass;
 import nu.marginalia.service.ServiceId;
@@ -38,8 +40,17 @@ public class AssistantMain extends MainClass {
         var configuration = injector.getInstance(ServiceConfiguration.class);
         orchestrateBoot(registry, configuration);
 
-        injector.getInstance(AssistantMain.class);
+        var main = injector.getInstance(AssistantMain.class);
         injector.getInstance(Initialization.class).setReady();
 
+        Jooby.runApp(new String[] { "application.env=prod" }, ExecutionMode.WORKER, () -> new Jooby() {
+            {
+                main.start(this);
+            }
+        });
+    }
+
+    public void start(Jooby jooby) {
+        service.startJooby(jooby);
     }
 }

code/services-core/assistant-service/java/nu/marginalia/assistant/AssistantService.java

@@ -2,27 +2,27 @@ package nu.marginalia.assistant;
 
 import com.google.gson.Gson;
 import com.google.inject.Inject;
+import io.jooby.Context;
+import io.jooby.Jooby;
 import nu.marginalia.assistant.suggest.Suggestions;
 import nu.marginalia.functions.domains.DomainInfoGrpcService;
 import nu.marginalia.functions.math.MathGrpcService;
 import nu.marginalia.livecapture.LiveCaptureGrpcService;
 import nu.marginalia.model.gson.GsonFactory;
 import nu.marginalia.rss.svc.FeedsGrpcService;
-import nu.marginalia.screenshot.ScreenshotService;
 import nu.marginalia.service.discovery.property.ServicePartition;
 import nu.marginalia.service.server.BaseServiceParams;
-import nu.marginalia.service.server.SparkService;
+import nu.marginalia.service.server.JoobyService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import spark.Request;
-import spark.Response;
-import spark.Spark;
 
 import java.util.List;
 
-public class AssistantService extends SparkService {
+public class AssistantService extends JoobyService {
     private final Logger logger = LoggerFactory.getLogger(getClass());
     private final Gson gson = GsonFactory.get();
+    @org.jetbrains.annotations.NotNull
+    private final ScreenshotService screenshotService;
     private final Suggestions suggestions;
 
     @Inject
@@ -39,30 +39,30 @@ public class AssistantService extends SparkService {
                 List.of(domainInfoGrpcService,
                         mathGrpcService,
                         liveCaptureGrpcService,
-                        feedsGrpcService));
+                        feedsGrpcService),
+                List.of());
+        this.screenshotService = screenshotService;
 
         this.suggestions = suggestions;
 
-        Spark.staticFiles.expireTime(600);
-
-        Spark.get("/screenshot/:id", screenshotService::serveScreenshotRequest);
-        Spark.get("/suggest/", this::getSuggestions, this::convertToJson);
-
-        Spark.awaitInitialization();
     }
 
-    private Object getSuggestions(Request request, Response response) {
-        response.type("application/json");
-        var param = request.queryParams("partial");
-        if (param == null) {
+    public void startJooby(Jooby jooby) {
+        super.startJooby(jooby);
+
+        jooby.get("/suggest/", this::getSuggestions);
+        jooby.get("/screenshot/{id}", screenshotService::serveScreenshotRequest);
+    }
+
+    private String getSuggestions(Context context) {
+        context.setResponseType("application/json");
+        var param = context.query("partial");
+        if (param.isMissing()) {
             logger.warn("Bad parameter, partial is null");
-            Spark.halt(500);
+            context.setResponseCode(500);
+            return "{}";
         }
-        return suggestions.getSuggestions(10, param);
-    }
-
-    private String convertToJson(Object o) {
-        return gson.toJson(o);
+        return gson.toJson(suggestions.getSuggestions(10, param.value()));
     }
 
 }

code/services-core/assistant-service/java/nu/marginalia/assistant/ScreenshotService.java

@@ -0,0 +1,118 @@
+package nu.marginalia.assistant;
+
+import com.google.common.base.Strings;
+import com.google.inject.Inject;
+import com.zaxxer.hikari.HikariDataSource;
+import io.jooby.Context;
+import nu.marginalia.db.DbDomainQueries;
+import org.apache.commons.io.IOUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.sql.SQLException;
+
+public class ScreenshotService {
+
+    private final DbDomainQueries domainQueries;
+    private final HikariDataSource dataSource;
+
+    private final Logger logger = LoggerFactory.getLogger(getClass());
+
+    @Inject
+    public ScreenshotService(DbDomainQueries dbDomainQueries, HikariDataSource dataSource) {
+        this.domainQueries = dbDomainQueries;
+        this.dataSource = dataSource;
+    }
+
+    public boolean hasScreenshot(int domainId) {
+        try (var conn = dataSource.getConnection();
+             var ps = conn.prepareStatement("""
+                    SELECT TRUE
+                        FROM DATA_DOMAIN_SCREENSHOT
+                        INNER JOIN EC_DOMAIN ON EC_DOMAIN.DOMAIN_NAME=DATA_DOMAIN_SCREENSHOT.DOMAIN_NAME
+                        WHERE EC_DOMAIN.ID=?
+                    """)) {
+            ps.setInt(1, domainId);
+            var rs = ps.executeQuery();
+            if (rs.next()) {
+                return rs.getBoolean(1);
+            }
+        }
+        catch (SQLException ex) {
+            logger.warn("SQL error", ex);
+        }
+        return false;
+    }
+
+    public Object serveScreenshotRequest(Context context) {
+        if (Strings.isNullOrEmpty(context.path("id").value(""))) {
+            context.setResponseCode(404);
+            return "";
+        }
+
+        int id = context.path("id").intValue();
+
+        try (var conn = dataSource.getConnection();
+             var ps = conn.prepareStatement("""
+                    SELECT CONTENT_TYPE, DATA
+                        FROM DATA_DOMAIN_SCREENSHOT
+                        INNER JOIN EC_DOMAIN ON EC_DOMAIN.DOMAIN_NAME=DATA_DOMAIN_SCREENSHOT.DOMAIN_NAME
+                        WHERE EC_DOMAIN.ID=?
+                    """)) {
+            ps.setInt(1, id);
+            var rsp = ps.executeQuery();
+            if (rsp.next()) {
+                context.setResponseType(rsp.getString(1));
+                context.setResponseCode(200);
+                context.setResponseHeader("Cache-control", "public,max-age=3600");
+
+                try (var rs = context.responseStream()) {
+                    IOUtils.copy(rsp.getBlob(2).getBinaryStream(), rs);
+                }
+                return "";
+            }
+        }
+        catch (IOException ex) {
+            logger.warn("IO error", ex);
+        }
+        catch (SQLException ex) {
+            logger.warn("SQL error", ex);
+        }
+
+        context.setResponseType("image/svg+xml");
+
+        var name = domainQueries.getDomain(id).map(Object::toString)
+                .orElse("[Screenshot Not Yet Captured]");
+
+        return """
+                <?xml version="1.0" encoding="UTF-8" standalone="no"?>
+                <svg
+                   xmlns="http://www.w3.org/2000/svg"
+                   width="640px"
+                   height="480px"
+                   viewBox="0 0 640 480"
+                   version="1.1">
+                  <g>
+                    <rect
+                       style="fill:#808080"
+                       id="rect288"
+                       width="595.41992"
+                       height="430.01825"
+                       x="23.034981"
+                       y="27.850344" />
+                    <text
+                       xml:space="preserve"
+                      style="font-size:100px;fill:#909090;font-family:sans-serif;"
+                       x="20"
+                       y="120">Placeholder</text>
+                    <text
+                       xml:space="preserve"
+                       style="font-size:32px;fill:#000000;font-family:monospace;"
+                       x="320" y="240" dominant-baseline="middle" text-anchor="middle">%s</text>
+                  </g>
+                </svg>
+                """.formatted(name);
+    }
+
+}